( 2G1 ) 



and rife up at fome diftance from it, and confequently appear larger 

 than they are in reality. * 



I know many people aix; of opinion that flies are produced from 

 corruption, and they pretend to bring many inftances in fupport of 

 that notion, which occuned to me lately in converfation with a cer- 

 tain learned gentleman, who argued thus upon the fubject : 



" I have obferved," fays he, " in a parcel of grubs or av^relias, 

 " produced from fome caterpillars of the fame fpecies, four butter- 

 " flies produced, all of the fame kind and fliape, and from the fifth 

 " aurelia, which had an aperture like the others and was tranfpa- 

 *' rent within, three common Flies illued. The caufe of this ap- 

 *' pearance 1 could not account for." 



Tq this gentleman I made anfwer, that thefe reafonings of his 

 made no difficulty with me, becaufe I conceived the matter might 

 be accounted for as follows : 



Flies, and almotl all living creatures which are not able to nou- 

 rifli their own young, have it implanted in them by Nature to lay 

 their eggs in thole places where the young, when hatched, may 

 find food. When, therefore. Flies of any description cannot find 

 any flefli, fifli, or ofl'al, they often lay their eggs in thofe places where 

 their infl:incl informs them their young will find fubfillence, and this 

 is in the grubs or aurelias of caterpillars; the maggots hatched from 

 thefe eggs laid by the Fly can ealily perforate the thin coat or cafe 

 of the aurelia, and ufc for their nourilhment that fubllance within 

 it, which was deftined to the formation of a winged creature of a 

 dilFerent fpecies, fo that from fuch an aurelia a Fly inftead of a but- 

 terfly may be produced. With this argument of mine the gentle- 

 man declared himfelf to be fatisfied. 



Now, I lay it down for a certain truth that it is equally impofiible 

 for a Fly, or other living animal, to be produced from corruption, 

 as for rocks to bring forth horfes or other beafis. 



* Anotlier rcafon may be affigned for this appearance, namely, the rapid growth of fly. 

 ing 'nfcfti iinmodi ifcly after thoir coming forih from their aurelia ilate. See the Tranflator's 

 remark on this fubject in a note. Vol. I. p. 28. 



